Mouldable hydrocolloid adhesive compositions

ABSTRACT

A mouldable pressure-sensitive hydrocolloid adhesive composition, particularly useful as a medical adhesive, comprising a dispersion of a discontinuous phase of one or more water-soluble and/or water swellable absorbent polymers in a continuous phase comprising a thermoplastic elastomer, a compatible liquid rubber, a polyisobutylene and a low-molecular weight polybutene.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Phase Patent Application of InternationalApplication No. PCT/GB02/01766, filed on Apr. 17, 2002, which claimspriority of British Patent Application No. 0110284.7, filed on Apr. 26,2001.

Hydrocolloid pressure sensitive adhesives are comprised of dispersionsof fluid absorbent materials in pressure sensitive adhesive matrices.These adhesives are well known in medical fields where they find use asmultifunctional components of medical devices. In particular,hydrocolloid adhesives have been extensively utilised in the fields ofostomy care and wound care. In ostomy care, hydrocolloid adhesives areused as the barrier adhesive to hold the pouch in place on theperistomal skin, and to protect this skin from the excoriating effectsof body waste. In wound care, hydrocolloid adhesives have been used asthe basis of absorbent dressings for direct application to especiallychronic wounds.

Hydrocolloid compositions are normally not very flexible or conformable,so that adhesion to movable and curved body parts is difficult. Thislack of flexibility can give rise to problems. For example, an ostomypatient with folded or scarred skin in the region of his stoma may havedifficulty in adhering the hydrocolloid adhesive of his pouch to theperistomal skin without getting a leak between the skin and theadhesive. Leaks would allow highly irritating and excoriating faeces orurine to come into contact with the skin. The present invention isdirected at new hydrocolloid adhesives that overcome some of theseproblems of the prior art adhesives, and extend the utility ofhydrocolloid adhesives into new application areas. Specifically, thisinvention is directed at hydrocolloid adhesives that are mouldable, andthat can be readily adapted to curved and movable body parts.

The prior art discloses products designed to overcome the shortcomingsof inflexible hydrocolloid skin barriers. In the field of ostomy care,adjunct products such as ostomy paste are well known. Such products areuseful for protecting and treating the skin contiguous to a stoma. Theproblem of fluid leakage is often aggravated where the skin around thestoma is irregular, or where folds of skin occur in this area. To obtainan improved seal the ostomate can apply a coating of paste in a ringaround the stoma, allow the paste to dry, and then apply the ostomypouch over the dried paste.

A number of ostomy paste compositions appear in the prior art. Forexample, British Patent Specification 1,430,515 to Hollister, Inc., U.S.Pat. No. 4,350,785 to Hollister Inc. and European Patent Application0048556 A1 to E. R. Squibb & Sons, all describe combinations of filmforming polymers with water absorbable hydrocolloid powders to form apaste which is dispensable from a tube. The problem with thesecompositions is that they have to have a viscosity low enough for theuser to squeeze them from the tubes and therefore they contain asolvent, usually an alcohol such as isopropanol or ethanol, which cansting the skin on application. Also, often the preparation can harden inthe tube, and become difficult or impossible to apply.

U.S. Pat. Nos. 4,166,051 and 4,204,540 suggest an alternative approachto the problem of securing an inflexible ostomy pouch barrier around thestoma of an ostomy patient with an irregular skin surface. These twopatents are directed to homogeneous compositions of a pressure sensitiveadhesive component, mineral oil, hydrocolloid gums and cohesivestrengthening agents, optionally with added elastomers such as butylrubber or medium molecular weight polyisobutylene. The putty-likecompositions can be shaped so as to fill the area between the stoma andthe skin barrier. The compositions can be employed to smooth an area ofthe abdomen around the stoma so as to provide a relatively flat surfaceto which an appliance or skin barrier can be securely attached. Theyhave the advantage over ostomy paste in that they do not containalcohol, and hence do not sting the skin upon application.

PCT International Application WO 98/17329 to Coloplast discloses amouldable mass of a putty-like adhesive for use in connection with anostomy appliance. The composition comprises 1-20 wt % of a blockcopolymer having a major content of di-block copolymer, 5-60 wt % of atackifying liquid constituent and 1-10 wt % of a waxy constituent. Theproduct can be extruded and slit into a rod form that can then be packedinto blisters. The rods can be protected with silicone release paper.Even though the composition is said to be removable from the skin as anintegrated unit, without leaving residues, the composition suffers fromthe drawback of being very sticky, and difficult to use because of itstackiness.

Eakin Cohesive, a hydrocolloid product available from T. G. Eakin &Sons, Comber, Northern Ireland, is said to be a mouldable, easilyshaped, moisture absorbing skin barrier. According to informationextracted from the Eakin website, http://www.eakin.co.uk, it can bestretched, compressed or moulded to fit the exact shape and size asrequired. Eakin Cohesive contains no active ingredients but is said tocontain a unique carbohydrate which is slowly released while the seal isin place, diluting harmful enzymes, and protecting the skin against bodywastes and fluids such as bile and ileal fluid. The product can be usedas a seal under stoma pouches and appliances, as a packing agent in skinfolds and scars, as a seal around drain tubes and fistulae, and as a“picture frame” around wound edges prior to dressing application. EakinCohesive is, however, not recommended for use in open wounds.

Eakin Cohesive is functionally comparable to ostomy pastes in that bothproducts can be moulded and formed to fill up scar areas and help toproduce a flat skin surface. However, although Eakin Cohesive Seals andostomy pastes perform the same or similar functions, there arefundamental differences in their performance. Patient studies revealedthat Cohesive Seals are easier to store, handle, mould, apply and removefrom the skin. In general they were quicker and easier to use than theostomy pastes and patients felt more comfortable and confident whenwearing them. Average pouch wear time was increased with use of theEakin Cohesive.

In comparison, the ostomy pastes were found to be messy to use, left aresidue on the skin, and were uncomfortable to remove. Ostomy pasteswere also noticeably less effective at improving the condition of red orexcoriated skin.

These patient studies show that a mouldable adhesive or putty such asthe Cohesive product is a better solution than is ostomy paste to theproblem of uneven skin in the peristomal area. Notwithstanding theseadvantages, however, there are several drawbacks with the Eakin Cohesiveproduct. It preferably has to be warmed to body temperature before use.If the seal is not warmed, it may appear to “crumble” and will be moredifficult to mould. Cohesive is not an integrated hydrocolloid. Thismeans that in the presence of body fluid such as faeces, urine or woundexudate, the composition breaks down to give a soft gel and becomesamorphous as it gets saturated with fluid. It is therefore an objectiveof the present invention to make an improved mouldable hydrocolloid forostomy care.

Eakin Cohesive cannot be used in direct contact with wounds. A mouldablehydrocolloid adhesive that could be used in the presence of exudingwounds would find utility as a wound packing, and provide a means ofextending the duration of wear of conventional hydrocolloid dressings,especially in the presence of wound exudate.

European Patent EP 0 651 983 B1 discloses a trimmable wound dressing inwhich a spiral of hydrocolloid is unwound to make a rope of rectangularcross section which can be used to pack a wound. The compositionscontain about 20 wt % elastomer and are elastic and not mouldable. Onthe contrary, they are said to retain their shape in use. Such astructure will expand in the wound as it absorbs wound exudate and,because of its relatively high elastic modulus, may exert considerablepressure on the wound bed.

It is therefore a further objective of the present invention to make amouldable hydrocolloid that is suitable for direct contact with wounds,and that will readily conform to wound cavities.

Ostomates who have a retracted stoma, or whose stoma is difficult topouch because it is hidden by folds of skin, can have additionalproblems with leaky appliances. In order to help to deal with thisproblem, pouches with convex faceplates have been developed. The convexfaceplate, especially when pressed around the stoma by means of a beltworn around the body and attached to either side of the pouch adhesiveflange, causes the retracted stoma to protrude further into the pouch,thus reducing the propensity for pouch leakage. The use of convexfaceplates in the design of ostomy pouches is becoming more common, andthe markets for them are growing. The manufacture of convex ostomyproducts would be facilitated with the use of mouldable hydrocolloids,which can be formed around a plastic convex plate under the influence ofheat and pressure. It is therefore still a further objective of thepresent invention to formulate a hydrocolloid adhesive that is suitablefor fabrication into an ostomy barrier having a convex faceplate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood when considered in light of thefollowing detailed description and the appended drawings, wherein:

FIG. 1 is a graphical comparison of the penetration test performance of(a) a mouldable hydrocolloid adhesive corresponding to one embodiment ofthe invention (Ex. 6) and (b) a known product (Eakin Cohesive); and

FIG. 2 is a schematic illustration of a convex body-side flange of atwo-piece ostomy device, together with a cross-sectional view thereof.

We have found very unexpectedly that hydrocolloid compositionscontaining small amounts of thermoplastic elastomer, and tackified withliquid rubbers for example as disclosed in U.S. Pat. No. 5,274,036,provide the basis for mouldable compositions more mouldable than EakinCohesive and that show no inclination to crumble at room temperature.Some of these compositions are moreover very highly integrated. Specificembodiments of the invention can be used in direct contact with openwounds to provide mouldable compositions useful for wound packing thatallow versatile management of such wounds.

A mouldable composition according to the invention comprises acontinuous phase containing a mixture of a permanently tacky pressuresensitive adhesive, preferably a holt melt adhesive based on astyrene-containing thermoplastic clastomer and a liquid rubber, a lowmolecular weight polyisobutylene and a low molecular weight liquidpolybutene, and dispersed within the continuous phase a discontinuousphase of one or more water soluble and/or water swellable absorbentpolymers.

Suitable styrene-containing thermoplastic elastomers useful in thepractise of this invention include block copolymers based onstyrene-butadiene, styrene-isoprene or styrene ethylene-butylene. Also,a low styrene synthetic copolymer of butadiene and styrene, commonlycalled SBR rubber, can be used as the thermoplastic elastomer. Theelastomer may consist of linear or radial A-B-A block copolymers ormixtures of these A-B-A copolymers with simple A-B block copolymers.However, the proportion of A-B block copolymers in the mixture of A-B-Aand A-B block copolymers should not exceed about 85% by weight and lowerpercentages would normally be used.

The A-B-A block copolymers are of the type which consist of A blocksderived from styrene or one of its homologues and B blocks derived fromconjugated dienes, such as butadiene or isoprene, or from lower alkenessuch as ethylene or butylene. The radial A-B-A polymers useful in thisinvention are of the type described for example in U.S. Pat. No.3,281,383 and conform to the general formula (A-B)_(n)X, where A and Bcomprise blocks derived from monomers described above in connection withthe A-B-A copolymers, X is an organic or inorganic connecting moietyhaving a functionality of at least 2, and n is equal to thefunctionality of X. The A-B block copolymers useful in this inventioncomprise A and B blocks derived from monomers described above inconnection with the A-B-A copolymers.

Liquid rubbers useful in this invention are synthetic liquid isoprenerubber, depolymerised natural rubber, carboxyl terminated syntheticliquid isoprene-styrene rubber, hydroxyl terminated synthetic liquidisoprene rubber, hydrogentated liquid isoprene rubber, liquidisoprene-styrene copolymer, liquid isoprene-butadience copolymer andliquid butadiene-styrene copolymer. The liquid rubbers have a molecularweight of about 25,000 to about 50,000. Preferably, the liquid rubbershave a glass transition temperature of less than −-50° C., and a meltviscosity at 38° C. of from 500-10,000 poises. It will be appreciatedthat other liquid rubbers known in the art could be useful in thepresent invention.

The polyisobutylene component is exemplified by the Vistanex LM seriesof polyisobutylenes, available from Exxon Chemical Corporation, andwhich have Flory viscosity average molecular weights in the range 35,000to 70,000, and Brookfield viscosities at 175° C. within the range 20,000and 140,000 mPa.s.

The low molecular weight polybutene components are exemplified by theHyvis series of materials from BP, and by the Parapol series of productsfrom Exxon Chemical Corporation, and which have molecular weightsranging from 1000 to 3000, determined using test method AM-I 841-86, andkinematic viscosities at 100° C. within the range 180 and 3500 cSt, asmeasured by test method ASTM D445.

Normally a suitable processing stabiliser would also be included in thehot melt adhesive component. Suitable stabilisers useful in the practiseof the invention include those indicated for use with styrene-olef instyrene block copolymer thermoplastic elastomers such asorganophosphites and the so-called hindered phenols, but any suitablestabilisers may be employed. An example of an organophosphite stabiliseris tris(nonylphenyl) phosphite, available as Polygard HR manufactured byUniroyal. Particularly useful are the hindered phenols, Irganox 1010 andIrganox 565, manufactured by Ciba. Irganox 1010 is pentaerythritoltetrakis (3-(3, 5-di-tert-butyl-4-hydroxyphenyl)propionate. Irganox 565is 2, 6-di-tert-butyl-4-(4,6-bis(octylthio)-l, 3,5-triazin-2-ylamino)phenol. Stabilisers may be us or in combination, and suitableranges are from 0.3 1.5% by weight based on the total formulation. Thestabilisers are always added to the continuous phase, as is shown in theexamples.

Other optional ingredients such as tackifiers and plasticisers may beadded to the continuous phase, to modify tack and optimise adhesionproperties.

The hot melt adhesive component is comprised of the thermoplasticelastomer and the liquid rubber, both as defined above, and issubstantially resin free. Preferably this hot melt adhesive is formedwith a weight ratio of thermoplastic elastomer to liquid rubber of about1:0.5 to about 1:7. The amount of liquid rubber used is varied for thedesired degree of adhesiveness and tackiness of the pressure sensitiveadhesive

The amount of hot melt adhesive used in the compositions is such thatmouldability is not compromised. The composition should preferablycontain at least 1 wt. % of this component but if too much thermoplasticelastomer is present in the formulation, the compositions will be tooelastic to function as a mouldable material. The preferred upper limitof thermoplastic elastomer in the formulation is 5 wt %, more preferably3 wt % and most preferably 2 wt %. In addition, the amount of liquidrubber is also important, and a maximum amount of liquid rubberemanating from the intermediate hot melt adhesive corresponding to 10 wt% of the total formulation is permitted. Preferably, the maximum amountof liquid rubber is limited to 8 wt % of the total formulation.

The polyisobutylene component may be present in an amount from 25 wt %to 45 wt % of the total formulation, preferably from 30 wt % to 40 wt %of the total formulation.

The low molecular weight polybutene may be present in an amount from 5wt % to 20 wt % of the total formulation, and preferably from 7 wt % to15 wt %.

The discontinuous phase comprises one or more hydrophilic polymers thatare soluble or insoluble but swellable in water as themoisture-absorbing component. One or more swellable polymers may bepresent. Suitable insoluble swellable polymers include cross-linkedsodium carboxymethyl cellulose, crystalline sodium carboxymethylcellulose, cross-linked dextran and starch-acrylonitrile graftcopolymer. The swellable polymer may also be a so- called “superabsorbent” material such as starch sodium polyacrylate. Other hydratablepolymers such as gluten and polymers of methyl vinyl ether and maleicacid and derivatives thereof may also be included in the discontinuousphase. Suitable water soluble polymers include sodium carboxymethylcellulose, pectin, gelatIne, guar gum, locust bean gum, collagen, karayagum and starch, particularly maize starch, and the like. Thediscontinuous phase should not normally exceed 60% of the total weightof the adhesive, preferably does not exceed 55% by weight of theadhesive, and more preferably does not exceed 50% by weight of theadhesive, and may be comprised of any combination of soluble and/orinsoluble absorbents.

Optional fillers such as silica and pigments and optional activeingredients such as antimicrobial compounds may also be incorporatedinto the compositions of the invention. Silver sulfadiazine andbenzalkonium chloride represent non-limiting examples of suchantimicrobial ingredients.

The adhesive compositions of the invention may be prepared as follows.The thermoplastic elastomer and the liquid rubber component are blendedtogether in a suitable mixer, normally a sigma blade mixer with anextruder discharge. The mixer is heated to about 170° C. A nitrogen flowof about 60 ml/sec through the mixer reduces the possibility ofoxidative degradation of the rubber during processing. About 1% phr of asuitable stabiliser, such as Irganox 1010 available from Ciba-Geigy, canbe added at this stage. The thermoplastic elastomer is allowed first toblend in the mixer until it coalesces. Normally a small amount of theliquid rubber, for example, 10-20% to the whole amount of thethermoplastic elastomer and the liquid rubber is allowed to blend withthe softened thermoplastic elastomer. When all this 10-20% of the liquidrubber has been absorbed, another portion of the liquid rubber is added,for example, 20-30%, and the liquid rubber is absorbed into thestyrene-olefin-styrene rubber. This is continued until all the liquidrubber is added, when a pourable tacky intermediate adhesive isobtained. The mixer blades are stopped, the direction of the screw isreversed, and the intermediate adhesive is removed from the mixer. It isrun off into suitable release coated containers and allowed to cool.

The mixer is cleaned, stabilised at 90° C. and the powdery hydrocolloidingredients are charged to the mixer together with the polyisobutylene.These are blended until uniform for about 10 minutes and then thepreviously blended hot melt adhesive component is added and the mixertemperature is raised to 105° C. After mixing at 105° C. for 15 min thetemperature of the mixer is dropped to about 80° C. and the lowmolecular weight polybutene is added. Mixing is continued normally for afurther 20 minutes or so. The fully mixed mass is then removed from themixer. It can then be extruded or pressed to the desired thickness,laminated to suitable substrates and die cut to shapes if needed.

The above manufacturing process has been described with respect to atwo-step process in which the hot melt adhesive comprising thestyrene-containing thermoplastic elastomer and the liquid rubber and thestabiliser is first manufactured and isolated and which is thensubsequently used to make the compositions of the invention. It will beappreciated by anyone skilled in the art that no process limitation isimplied and the adhesives of the invention may equally well be preparedin a one-pot process, with no isolation of the intermediate hot meltadhesive.

The following test methods were used to characterise the products.

Static Absorption of Hydrocolloids

To determine the amount of fluid uptake into a known surface area ofhydrocolloid adhesive.

Procedure

Cups with flanges for use in determination of Moisture VapourTransmission are suitable for use in this test. Laminate release linerto the upper flange of the cup with the double coated tape. This is thecontact zone for the hydrocolloid. Fill the cup with 30 ml NaCl solution(0.9% wt). Cut a sample of hydrocolloid of about the same size as theouter cup diameter. Weigh the sample (W₁). Laminate the sample to thecup, making sure that the seal between the hydrocolloid sample and thecup is water tight. Turn the cup upside down and put it in the oven at37° C. for 24 hours. Cool down. Remove the hydrocolloid from the cup andreweigh (W₂). Calculate the water fluid absorption (g/sq. m. 24 h) usingthe formula:absorption=(W ₂ −W ₁)/0.002375where the area of the hydrocolloid in contact with salt solution is0.002375 sq. m.Determination of the Integrity

The integrity of a hydrocolloid is defined as its ability to resistbreakdown by biological fluids. The test measures the weight percentageof hydrocolloid retained after exposure to saline under specifiedconditions.

Procedure

Condition the hydrocolloid samples at 23±1° C. and 50±2% relativehumidity for 24 hours. Cut circular samples from the hydrocolloid sheet2.54 cm diameter. Weigh and record the samples (W_(i)). Place eachsample in a 120 ml (4 oz) bottles with screw caps (Vel Catalog Number1198017) with 50 ml physiological saline (NaCl 0.9% wt in water), capthe bottles and agitate on a bottle shaker at maximum speed for a periodof 18 hrs. Remove the samples and dry them in a circulating air oven at50° C. and 50% relative humidity until dry. This usually takes about 24hours. Reweigh the sample (W_(f)). The Integrity Value of the sample iscalculated using the following equation:

${{Integrity}\mspace{14mu}{Value}\mspace{11mu}(\%)} = {100 \times \frac{( W_{f} )}{( W_{i} )}}$Note: The test may be run with hydrocolloid with or without carrier.However, the result may be affected, and suitable control samples shouldalways be included.Determination of Mouldability

Assessment of the mouldability of the hydrocolloid materials was madeusing the test methods described in Adhesives Age, September 1997, pp18-23. The equipment used was a probe tester manufactured by StableMicro Systems, Godalming, Surrey, England, driven by custom designedsoftware.

Using the equipment, the energy absorbed by the mouldable adhesive asthe probe penetrated the adhesive was determined by a transducer. Theprobe is moved up and down by a rotating screw which is driven by astepping motor. The displacement of the probe was measured through themotor rotation.

For each measurement, the probe was a stainless steel ball of 25.4 mm indiameter. The compressive force was 4.5N and the test speed was 0.04mm/sec.

The raw materials used in the examples are as follows:

-   Escorez 2203LC—Exxon Chemical—Tackifying resin-   Regalite 1100—Hercules Chemical—″ ″-   Adtac LV-E—Hercules Chemical—″ ″-   LVSI-101—Kraton Polymers—Liquid rubber-   Vector 4111—Exxon Chemical—Thermoplastic elastomer-   Kraton D-1161NS—Kraton Polymers—″ ″-   Irganox 1010—Ciba Chemicals—Antioxidant-   Parapol 1300—Exxon Chemical—Polybutene-   Vistanex LMMS—Exxon Chemical—Polyisobutylene-   Maize Starch—National Starch and Chemical-   Pectin USP100—Hercules Chemical-   Blanose 7H4XF—Hercules Chemical—Sodium carboxymethyl cellulose-   Aquasorb A500—Hercules Chemical—Sodium carboxymethyl cellulose-   Kaydol Mineral Oil—Witco Chemical

The invention will now be further described with reference to thefollowing non-limiting examples. While Examples 6 through 12 illustratethe application of the present invention to constructions generallysuitable for use in ostomy care, and Examples 13 through 27 showformulations generally more suitable for use in wound care applications,it will be understood that no limitation is implied by this separation.

EXAMPLE 1

This example illustrates preparation of the intermediate hot meltadhesive.

wt % total Amount, gm LVSI-101 79.37 400 Kraton KD-1161N 19.84 100Irganox 1010 0.79 4 100.00 504

A Z-blade mixer of 1 kg. capacity was purged with nitrogen gas andheated to 160° C. The speed of the front, faster, blade was 30 rpm. TheKraton KD-1161N and the Irganox 1010 were charged to the Mixer at 160°C., and the mixer was started. After mixing for 5 minutes, the rubberycrumb coalesed, and 50 gm of the LVSI-101 was added with continuedmixing and nitrogen purging. After a further ten minutes, thetemperature was raised to 170° C. and the mixer front blade speedincreased to 47 rpm. The LVSI had at this point completely mixed withthe rubber, and a further 51 gm of LVSI was added. Ten minutes later,after blending of the second portion of the LVSI, a further 48 gm ofLVSI was added, and mixed for a further 10 minutes. In this way,approximately 50 gm portions of the charge of LVSI were added every 10minutes until all the 400 gm had been added. 15 minutes later, theintermediate adhesive was dumped from the mixer. The total time for thisoperation was about 90 minutes.

EXAMPLE 2

In a similar way to Example 1, the following adhesive was made.

wt % total Amount, gm LVSI-101 59.54 300 Kraton KD-1161N 39.68 200Irganox 1010 0.80 4 100.02 504

EXAMPLE 3

This example illustrates the preparation of a more conventional hot meltadhesive used in the formulations. The mixer was purged with nitrogengas and heated to 160° C. The Regalite R1100, 200 gm. and the Irganox1010 were charged to the mixer at 160° C., and warmed for 15 minutes.The amount of Vector 4111 triblock S-I-S elastomer from Exxon Chemicalwas added. After mixing for 70 minutes, the remainder of the Regaliteand the Adtac LV-E were added over 35 minutes. The adhesive was run offfrom the mixer into release coated containers and cooled.

wt % total Amount, gm Regalite R1100 45.08 362 Irganox 1010 0.75 6Vector 4111 36.11 290 Adtac LV-E 18.06 145 100.0 803

EXAMPLE 4-5

In an analogous fashion to Example 3, two further intermediate adhesiveswere prepared having the following compositions:

wt % total Amount, gm Example 4 Escorez 2203 LC 41.69 336 Irganox 10100.74 6 Kraton D-1161NS 37.72 304 Adtac LV-E 19.85 160 100.0 806 Example5 Regalite R1100 46.12 320.0 Irganox 1010 2.39 16.6 Kraton D-1161NS33.04 229.2 Mineral Oil 18.45 128.0 100.0 693.8

EXAMPLE 6

This example illustrates the manufacture of a mouldable hydrocolloidformulation suitable for use by ostomy patients as a filler for unevenskin under an ostomy pouch, and for conversion to a convex faceplatepouch barrier construction.

Maize Starch (96 gm), Pectin USP100 (40 gm) and sodium carboxymethylcellulose, Blanose 7H4XF (100 gm) were charged to a laboratory scale 1l.Z-blade mixer, previously heated to 90° C. After blending the powdersfor 2 minutes, Vistanex LMMS polyisobutylene (164 gm) was added, andmixing was continued for 10 minutes, at the end of which time thetemperature of the mixer was raised to 105° C. The hot melt adhesive2-18A from Example 1 (40 gm) was added to the mixer, and blending wascontinued for a further 10 minutes, at the end of which time thetemperature in the mixer was dropped to 85° C. Parapol 1300 (40 gm) wasadded gradually to the contents of the mixer and kneading was continuedfor 20 minutes after the final addition of the Parapol ingredient. Themixer was stopped and the hydrocolloid was removed. It was extruded in alaboratory extruder between two silicone coated release papers to a webof 2.4 mm thickness.

The mouldable hydrocolloid was evaluated and found to have an absorbencyof 7742 Gms/sq. m./24 hrs, and an integrity of 93.8%. The results areshown in TABLE 1.

EXAMPLES 7-10

In an analogous fashion to Example 6, mouldable hydrocolloids ofExamples 7-10 were made and evaluated, with the results shown in theTABLE 1 below.

TABLE 1 Formulation, wt % Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Hot Melt of 1 23 5 4 Example LVSI-101 6.61 4.96 — — — Kraton 1.65 3.31 — 2.75 3.14D-1161NS Vector 4111 — — 3.01 — — Irganox 1010 0.07 0.07 0.06 0.20 0.06Regalite 1100 — — 3.76 3.84 — Adtac LV-E — — 1.50 — 1.65 Mineral Oil — —— 1.54 — Escorez 2203 — — — — 3.47 LC Vistanex LMMS 34.17 34.17 34.1734.17 34.17 Pectin USP100 8.33 8.33 8.33 8.33 8.33 Blanose 7H4XF 20.8320.83 20.83 20.83 20.83 Maize Starch 20.00 20.00 20.00 20.00 20.00Parapol 1300 8.33 8.33 8.33 8.33 8.33 Properties Liquid rubber: 4.001.50 (1.75) (1.40) (1.86) Thermoplastic elastomer, wt/wt Static 77426379 8295 7061 8290 Absorption Gms/sq. m./ 24 hrs Integrity, % 94 12 2010 10 Thickness, mm 2.4 2.0 2.0 2.0

The results from TABLE 1 are striking and show the surprising resultthat, at the low level of rubber used, only the one intermediate hotmelt adhesive used in Example 6 serves to integrate the hydrocolloid.Example 7 contains a higher amount of S-I-S thermoplastic elastomer, anda higher thermoplastic elastomer:liquid rubber ratio than does theadhesive of Example 6. The mouldable adhesives from comparative examples8, 9 and 10, which have no liquid rubbers, but rather containconventional tackifying agents, have very little integrity. The datashow that, in the adhesive system exemplified by Example 6, an upperrubber concentration limit of 2% by weight, and a thermoplasticelastomer:liquid rubber ratio of less than 1:1.5, and preferably 1:4,appears necessary to get integration.

EXAMPLE 11

The mouldable hydrocolloid from Example 6 was compared with the EakinCohesive product. The data on each are given in TABLE 2. It can beclearly seen that the integrity of the Eakin product is close to zero(the 10% integrity measured actually derives from the residual plasticfilm that was laminated to the product for the test). Typicalpenetration data are shown in the curves of FIG. 1. It can very clearlybe seen that the energy absorbed by the hydrocolloid of Example 6 is fargreater than that of the comparatively rigid Eakin Cohesive product,demonstrating the softness and easier mouldability of the hydrocolloidof Example 6. TABLE 2 shows also the greater penetration (21.5 mm) ofthe Example 6 adhesive by the stainless steel probe at the force of4.5N, compared to that with the Eakin Cohesive product (18.0 mm).Because of the poor integrity of the Cohesive, its absorption could notbe measured, as the adhesive melts into a soft, low viscosity gel. Theother measured properties of the two adhesives are comparable.

TABLE 2 Eakin Cohesive Ex. 6 Reverse tack, N/25 mm 9.1 12.0 PeelAdhesion 90° Teflon, N/25 mm 2.6 4.8 Shear Adhesion 0.5 kg, min 18 20Thickness, mm 2.60 2.45 stat. Absorption, gm/sq. m/24 hr Not Measurable7566 Penetration/Softness, mm 18.0 21.5 Integrity, % 10 98

The static absorption and the integrity of Example 6 in TABLE 2 differslightly from the values shown for Example 6 in TABLE 1, because theywere measured on a different batch of mouldable adhesive.

EXAMPLE 12

The hydrocolloid from Example 6 is made into a convex body-side flangeof a two piece ostomy-device, illustrated in FIG. 2. With reference tothe FIG. 2, component 13 is an injection moulded body-side flange piece,with an integral flange circumferential to the outer edge of the convexform. The body-side flange is moulded from a blend of low molecularweight polyethylene and ethylene-vinyl acetate copolymer. Component 11is an annular collar die cut from treated, waterproofed Sontara 8000non-woven fabric which is coated with medical grade acrylic pressuresensitive adhesive on its underside, and is available as Lasso SA72 fromSmith and Nephew, which can overlay the circumferential flange of theconnector. Component 12 is the mouldable hydrocolloid adhesive, mouldedto the underside of the convex flange and the non-woven overlay, using amatched die set which is heated to 100° C. in a 100 ton Bradley andTurton upstroking press. A vacuum moulded plastic protector, not shownin FIG. 2, with silicone release coating on its concave surface, can bemade to fit on the underside of the construction to protect the adhesiveuntil removal by the end-user.

EXAMPLES 13-27

Examples 13-27 show the formulation of mouldable hydrocolloids suitablefor direct contact with wounds. The results are shown in TABLES 3 and 4.Generally, starch is not considered suitable for contact with woundssince it is likely to be a nutrient for any pathogenic organismspresent. Aquasorb A500, crystalline sodium carboxymethyl celluloseavailable from Aqualon division of Hercules Chemical Company, generallywas used as a replacement for the starch in these compositions. Theformulations having the highest degree of integrity were integrated witha hot melt adhesive having a thermoplastic elastomer:liquid rubber ratioof 1:4. Examples 24-27 in comparison, with the same amount of hot meltadhesive but with a 1:1.5 ratio of thermoplastic elastomer:liquidrubber, were not found to have such high integrity. It was also foundthat the highest integrity products had, as the absorbent medium, blendsof soluble and insoluble absorbents. Nevertheless, these compositionsare also useful as mouldable hydrocolloid adhesives.

Example 23, when sterilised using gamma radiation at 25 KGy, showedexcellent retention of integrity, and a moderate but still acceptablereduction in absorption capacity. The gel resulting from absorption offluid is soft, will readily conform to the surface of a wound bed andwill not cause significant pressure within the wound.

TABLE 3 Formulation, wt % Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex.19 Ex. 20 Hot Melt of 1 1 1 1 1 1 1 1 Example LVSI-101 6.61 7.94 6.616.61 4.76 4.71 6.53 4.76 Kraton D-1161NS 1.65 1.98 1.65 1.65 1.19 1.181.63 1.19 Irganox 1010 0.07 0.08 0.07 0.07 0.05 0.05 0.07 0.05 VistanexLMMS 34.17 35.00 35.00 35.00 35.00 34.57 34.57 35.00 Pectin USP100 — —8.00 8.00 8.00 7.90 7.90 17.00 Blanose 7H4XF — — 20.00 20.00 20.00 19.7519.75 32.00 Aquasorb A500 49.16 45.00 17.00 18.67 17.00 20.74 16.79 —Parapol 1300 8.33 10.00 11.67 10.00 14.00 11.11 12.76 10.00 PropertiesLiquid rubber: 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 Thermoplasticelastomer, wt/wt Static Absorp 11760 12027 7992 7810 7478 8214 7512 8518Gms/sq. m./24 hrs Integrity, % 40 35 38 48 9 9 29 7 Thickness, mm 2.02.0 0.8 0.8 0.8 0.8 0.8 1.0

TABLE 4 Formulation, wt % Ex. 21 Ex. 22 Ex. 23 Ex. 23 Ex. 24 EX. 25 Ex.26 Ex. 27 Hot Melt of 1 1 1 1 2 2 2 2 Example Non- sterile sterileLVSI-101 6.61 7.94 7.94 7.94 5.95 5.95 5.95 5.95 Kraton D-1161NS 1.651.98 1.98 1.98 3.97 3.97 3.97 3.97 Irganox 1010 0.07 0.08 0.08 0.08 0.080.08 0.08 0.08 Vistanex LMMS 35.00 35.00 35.00 35.00 35.00 35.00 30.0032.50 Pectin USP100 15.00 15.00 8.00 8.00 — 8.00 — 8.00 Blanose 7H4XF30.00 30.00 20.00 20.00 — 20.00 — 20.00 Aquasorb A500 1.67 — 17.00 17.0045.00 17.00 45.00 17.00 Parapol 1300 10.00 10.00 10.00 10.00 10.00 10.0015.00 12.50 Properties Liquid rubber: 4.00 4.00 4.00 4.00 1.50 1.50 1.501.50 Thermoplastic elastomer, wt/wt Static Absorp 7562 7819 9006 654711865 9802 11254 7806 Gms/sq. m./24 hrs Integrity, % 59 70 78 74 10 1010 10 Thickness, mm 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

1. A convex body-side flange of an ostomy device, having formed thereona layer of a mouldable, pressure-sensitive, hydrocolloid adhesivecomposition comprising a continuous phase of a mixture of (a) athermoplastic elastomer, present in an amount of 1-5 wt. % of thecomposition, (b) a liquid rubber, wherein the weight ratio ofthermoplastic elastomer to liquid rubber is 1:0.5 to 1:7, (c)polyisobutylene having a viscosity-average molecular weight of from35,000-70,000, present in an amount of from 25-45 wt. % of thecomposition, (d) a low molecular weight liquid polybutene, present in anamount of from 5-20 wt. % of the composition; and a discontinuous phaseof one or more water-soluble and/or water swellable absorbent polymers.2. A convex body-side flange of an ostomy device according to claim 1,wherein the liquid rubber has a molecular weight of 25,000 to 50,000. 3.A convex body-side flange of an ostomy device according to claim 1,wherein the low molecular weight polybutene has a molecular weight of1,000 to 3,000 according to ASTM D445.
 4. A convex body-side flange ofan ostomy device according to claim 1, wherein the content ofthermoplastic elastomer, based on the total composition, is not morethan 3 wt. %.
 5. A convex body-side flange of an ostomy device accordingto claim 4 wherein the content of thermoplastic elastomer does notexceed 2 wt. %.
 6. A convex body-side flange of an ostomy deviceaccording to claim 1, wherein the content of liquid rubber does notexceed 10 wt. % of the composition.
 7. A convex body-side flange of anostomy device according to claim 1 wherein the polyisobutylene comprisesfrom 30-40 wt. % of the composition.
 8. A convex body-side flange of anostomy device according to claim 1, wherein the low molecular weightpolybutene comprises from 7-15 wt. % of the composition.
 9. A convexbody-side flange of an ostomy device according to claim 1, wherein thediscontinuous phase comprises not more than 60 wt. % of the totalcomposition.